Automated meter reading (AMR) and advanced metering infrastructure (AMI) are technologies used for the wireless monitoring and control of remote systems. Used by various utilities, these technologies allow users to centrally monitor and control the flow of resources to reduce environmental risks and efficiently manage operations.
Very low frequency (VLF) power line communications (PLC) presently has widespread use in AMR/AMI deployments and may also be useful for smart grid applications, largely due to its excellent propagative properties. However, noise within the VLF band is more energetic than at higher frequencies and without effective noise mitigation degrades channel capacity, possibly to the point of making the band impractical.
Paired transmission lines and other devices on the grid are not conducive to high frequency carrier signals. Signals within the VLF band (and those below it) have the advantage of propagating over very long distances. The TWACS communication system, resides within the extremely low frequency band (ELF) and has very little, if any, signal attenuation over distances up to 100 miles, for example. While successful low frequency band (LF) links have been demonstrated over distances of 2 to 6 km as have broadband links over distances of 1 km, in many deployments a complete substation-to-meter link cannot be established in these bands without introducing signal boosters or repeaters.
One disadvantage to using the VLF band is reduced data rate due to decreased available bandwidth. Another objection to VLF PLC is that the noise increases with decreasing frequency. Thus, while desirable propagative properties of the medium may yield high signal energies, the effect may be offset by a disproportionate increase in noise power.